The Russian president, Vladimir Putin, today repeated his warning that Moscow would view any attempt to expand Nato to its borders as a "direct threat".

Russia has been angered by the 26-nation military alliance's eastward growth, and Nato yesterday said Ukraine and Georgia, both former Soviet republics, could one day join.

The Nato secretary general, Jaap de Hoop Scheffer, said 90 minutes of talks on the final day of a three-day summit in Bucharest, Romania, had been "in a positive spirit", but added: "I cannot report that this morning we saw stunning breakthroughs."

Putin – who described the negotiations as constructive – agreed to allow Nato to cross Russian soil to deliver supplies including food and military equipment to its forces in Afghanistan.

However, that fell short of Nato hopes that Putin would also allow troops or air transit arrangements to pass through Russia.

Before today's negotiations, there had been optimism that the talks would result in land and air corridors for troops and equipment and boost cooperation on training local counter-narcotics officials.

The Nato summit comes ahead of talks between Putin and the US president, George Bush, in the Russian resort of Sochi on Sunday.

The pair have already outlined a potential deal to avert a crisis over Washington's planned missile defence system in Europe, involving a string of safeguards to ensure it could not be used against Russia.

Bush has insisted the system is a shield against a potential Iranian missile attack on Europe or the US, but Moscow sees it as an attempt to blunt Russia's nuclear deterrent.

Officials on both sides say the row is the biggest factor behind the current chill in east-west relations.

The US president will go into Sunday's bilateral summit armed with two important bargaining counters won in Bucharest yesterday.

Washington gained formal Nato support for the anti-ballistic missile scheme and also nailed down an agreement with the Czech government to build a missile-tracking radar on its soil.